1. Field of the Invention
The present invention relates to a compressor built in an air conditioner in a vehicle or the like.
This application is based on Patent Application No. Hei 9-363831 filed in Japan, the contents of which are incorporated herein by reference.
2. Description of the Related Art
FIG. 2 shows an example of a conventional scroll-type compressor. In this figure, reference numeral 1 indicates a housing which comprises cup-like main body 2, and front housing 6 fastened to the body 2 using a bolt (not shown). Rotational shaft 7 is supported by the front housing 6 via bearings 8 and 9, in a freely rotatable relationship.
Fixed scroll 10 and revolving scroll 14 are provided inside the housing 1. This fixed scroll 10 comprises end plate 11 and spiral lap 12 disposed on surface 11a of the plate 11, and the surface faces end plate 15 which is explained later. The end plate 11 is fastened to cup-like main body 2 via bolt 13.
In the above structure, the outer-peripheral surface of the end plate 11 is in close contact with the inner-peripheral surface of the cup-like main body 2, and thereby internal partitioning of housing 1 is established in a manner such that discharge cavity 31 is limitedly provided outside the end plate 11, while suction chamber 28 is limitedly provided inside the end plate 11.
On the other hand, a central part of end plate 11 is bored to provide discharge port 29, and opening and closing operations of this discharge port 29 are performed using discharge valve 30. The rising motion of discharge valve 30 is restricted by valve presser 32, and one end of both discharge valve 30 and valve presser 32 is fastened to end plate 11 via bolt 33.
The revolving scroll 14 comprises end plate 15 and spiral lap 16 which is disposed on surface 15a of the plate 15, and the surface faces the end plate 11. This spiral lap 16 has substantially the same shape as spiral lap 12 included in fixed scroll 10. The axes of the revolving and fixed scrolls 14 and 10 are separated from each other by a predetermined distance, that is, they are in an eccentric relationship. In addition, the phases of these scrolls differ by 180.degree., and they are engaged with each other as shown in FIG. 2.
Accordingly, tip seals 17, provided and buried at each head surface of spiral lap 12, are in close contact with surface 15a of end plate 15, while tip seals 18, provided and buried at each head surface of spiral lap 16, are in close contact with surface 11a of end plate 11. The side faces of spiral laps 12 and 16 make linear contact at plural positions and thus plural compression chambers 19a and 19b are formed essentially at positions of point symmetry with respect to the center of the spiral.
Inside projecting disk-shaped boss 20, provided at a center area in the outer surface (opposite to inner surface 15a) of end plate 15, drive bush 21 is inserted in a freely rotatable state via revolving bearing 23. Slide hole 24 is provided in the drive bush 21, and eccentric drive pin 25 is inserted into the slide hole 24 so as to perform a freely-sliding motion of the pin. The projecting drive pin 25 is eccentrically provided on an end face of larger-diameter portion 7a of rotational shaft 7, the portion 7a being provided on an end of the main body 2 side of the rotational shaft 7.
Between the peripheral edge of the outer surface of end plate 15 and an inner end face of front housing 6, thrust bearing 36 and Oldham link 26 are inserted.
In order to balance a dynamically unbalanced situation due to a revolving motion of the revolving scroll 14, balance weight 27 is attached to drive bush 21, and balance weight 37 is attached to the rotational shaft 7.
According to the above structure, when the rotational shaft 7 is rotated via clutch 3 which is connected with the shaft, revolving scroll 14 is driven via a revolving-radius variable mechanism consisting of eccentric drive pin 25, slide hole 24, drive bush 21, revolving bearing 23, boss 20, etc. The revolving scroll 14 revolves along a circular orbit having a radius of revolution, while rotation of the scroll 14 is prohibited by the Oldham link 26.
In this way, the above-mentioned line-contact portions in the side faces of spiral laps 12 and 16 gradually move toward the center of the "swirl", and thereby compression chambers 19a and 19b also move toward the center of the swirl while the volume of each chamber is gradually reduced.
Accordingly, gas, which has flowed into suction chamber 28 through an inlet (not shown), enters from an opening which is limited by the outer peripheral edges of spiral laps 12 and 16 to compression chambers 19a and 19b. This gas is gradually compressed and reaches central chamber 22. From the central chamber, the gas passes through discharge port 29, and presses and opens discharge valve 30, and thereby the gas is discharged into discharge cavity 31. The gas is then discharged outside via an outlet not shown.
If the above conventional scroll-type compressor is accelerated very rapidly under operational conditions with a high compression ratio, the temperature of compression chambers 19a and 19b also rises rapidly. Accordingly, both spiral laps 12 and 16 are thermally expanded, and the length of the teeth thereof also extends. However, the rise in the temperature of the housing 1 to which the fixed scroll 10 and revolving scroll 14 are attached is relatively slow; thus, expansion of the housing is also relatively small. As a result, the heads of spiral laps 12 and 16 may be tightly contacted with inner surfaces 15a and 11a of end plates 15 and 11, and accordingly, seizure or scuffing may occur at the contact section.